A.T. Robertson Commentary Matthew 13:31

"Another parable set he before them, saying, The kingdom of heaven is like unto a grain of mustard seed, which a man took, and sowed in his field:" — Matthew 13:31 (ASV)

Is like (ομοια εστιν). Adjective for comparison with associative instrumental as in 13:13,44,45,47,52.

Grain of mustard seed (κοκκω σιναπεως). Single grain in contrast with the collective σπερμα (17:20).

Took and sowed (λαβων εσπειρεν). Vernacular phrasing like Hebrew and all conversational style. In Koine.